1. Field of the Invention
The present invention relates to mine roof bolts. Specifically, the present invention relates to flexible mine roof bolts utilizing a multi-strand cable and which are adapted to be rotated in the bore hole by a drive head at a first end thereof.
2. Description of the Prior Art
Flexible cable bolts and cable systems have been utilized in the construction and mining industries since about 1970. More recently, cable mine roof bolts have been utilized as a roof control in the mining industry with both resin grouting and more conventional cement grouting techniques. Examples of cable mine roof bolts, utilized in resin grouting applications, can be found in U.S. Pat. No. 5,230,589 to Gillespie; U.S. Pat. No. 5,259,703 to Gillespie; U.S. Pat. No. 5,375,946 to Locotos; and WIPO Publication No. WO 93/03256 to Fuller et al. All of these mine roof bolt designs incorporate some type of drive head assembly for rotating the cable bolt. All of these prior art systems suffer from various drawbacks.
The mine roof bolt, disclosed in the Gillespie patents, replaces a tubular barrel of a conventional barrel and wedge assembly with a specially machined hexagonal head collar. The hexagonal head collar must necessarily be large enough to receive the internal wedges therein, which make the head collar too large to be driven with conventional bolting equipment. Consequently, in addition to the special machining of the hexagonal drive head, the Gillespie patents require the use of specialized adapters by the bolting equipment to accommodate the enlarged hexagonal head.
WIPO Publication No. WO 93/03256 and the Locotos patent disclose cable mine roof bolts which utilize a hex nut attached to the end thereof, to both rotate the cable bolt and support the bearing plate. The WIPO publication discloses inclusions of threads on at least one of the strands of the cable so that the hex nut can be threaded directly onto the cable. The Locotos patent utilizes a collar having a threaded end which is attached to the cable with the hex head threaded onto the collar. These designs require the attachment of the hex nut to the cable to meet the loading capacity of the cable bolt since the drive heads also serve to support the bearing plate.
It is the object of the present invention to provide a mine roof bolt design which overcomes the disadvantages of the above-described prior art. It is a further object of the present invention to provide a mine roof bolt design which can be utilized with conventional roof bolting equipment. A further object of the present invention is to provide a mine roof bolt which is easy and economical to manufacture.
The objects of the present invention are achieved by an embodiment of the present invention that provides a mine roof bolt which includes a flexible multi-strand cable, a barrel and wedge assembly attached to the cable between first and second ends thereof, and a drive head attached to the multi-strand cable at a position spaced along the cable from the barrel and wedge assembly, with the drive head having a plurality of driving faces on an exterior surface thereof.
In this embodiment, the drive head may be positioned adjacent to the barrel and wedge assembly, wherein the drive head extends less than one inch beyond the barrel and wedge assembly. Alternatively, the mine roof bolt of this embodiment may further include a sleeve member surrounding the cable which is formed integrally with the drive head. The sleeve member may be positioned to extend partially into the barrel of the barrel and wedge assembly. The sleeve member may be attached to the cable by swaging, adhesives, welding or combinations thereof. Additionally, the drive head may include a central bore therethrough for receiving the cable. The drive head may be secured to the cable by use of adhesives, a cable-spreading wedge or a combination thereof. A cable-spreading wedge may be inserted into a first end of the cable which is received within the bore of the drive head. The cable-spreading wedge will bias the outer strands of the cable against the drive head to secure the cable to the drive head.
These and other advantages of the present invention will be clarified in the brief description of the preferred embodiments, wherein like reference numerals represent like elements throughout.